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    $result;
}

sub delete {
    my ($self, $key) = @_;
    $self->cache->delete($key.":earlyexp");
    $self->cache->delete($key);
}

1;
__END__

=head1 NAME

Cache::Isolator - transaction and concurrency manager of cache systems.

=head1 SYNOPSIS

  use Cache::Isolator;
  use Cache::Memcached::Fast;

  my $isolator = Cache::Isolator->new(
      cache => Cache::Memcached::Fast->new(...),
      concurrency => 4,
  );

  my $key   = 'query:XXXXXX';
  $isolator->get_or_set(
      $key, 
      sub { # This callback invoked when miss cache
          get_from_db($key);
      },
      3600
  );

=head1 DESCRIPTION

Cache::Isolator is transaction and concurrency manager of cache systems. 
Many cache systems have Thundering Herd problem. If a cache has expired, concentration of access to the database may happen. This will cause a system failure. Cache::Isolator can control the concentration of load.

=head1 METHODS

=head2 new( %args )

Following parameters are recognized.

=over

=item cache

B<Required>. L<Cache::Memcached::Fast> object or similar interface object.

=item concurrency

Optional. Number of get_or_set callback executed in parallel.
If many process need to run callback, they wait until lock becomes released or able to get values.
Defaults to 1. It means no concurrency. 

=item interval

Optional. The seconds for busy loop interval. Defaults to 0.01 seconds.

=item trial

Optional. When the value is being set zero, get_or_set will be waiting until lock becomes released.
When the value is being set positive integer value, get_or_set will die on reached trial count.
Defaults to 0.

=item timeout

Optional. The seconds until lock becomes released. Defaults to 30 seconds.

=item early_expires_ratio

Optional. if early_expires_ratio was set to greater than zero, Cache::Isolator stores to duplicate the cache. One of them is set to expire earlier than normal. Cache::Isolator gets the cache has been set to expire early in the specified percentage. T...

  my $cache = Cache::Isolator->new(
      early_expires_ratio => 10, # This means 1/10 ratio
  );

=item expires_before

Optional. Seconds earlier expiration. Defaults is 10.

=back

=head2 get_or_set( $key, $callback, $expires )

$callback is subroutine reference. That invoked when cache miss occurred.

=head2 get($key)

=head2 set($key, $value, $expires)

=head2 delete($key)

=head1 AUTHOR

Masahiro Nagano E<lt>kazeburo {at} gmail.comE<gt>

=head1 SEE ALSO

=head1 LICENSE

This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.

=cut